<!DOCTYPE html>
<html lang="zh-CN">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<body>

    <div id="app">

        <button v-on:click="add">+</button>
        <button v-on:click="decrement">-</button>

        <span v-text="number"></span>
    </div>

    <script src="./node_modules/vue/dist/vue.js"></script>
    <script>
        var app = new Vue({
            el: '#app',
            data: {
                number: 0
            },
            methods: {
                add() {
                    this.number++;
                },
                decrement() {
                    this.number--;
                }
            }
        });
    </script>

</body>

</html>